Radio frequency filter, high selectivity triplexer, and communications device

Abstract

Communications devices, triplexers, high-pass filters, and low-pass filters are disclosed. A communications device includes a triplexer having a common port and first, second, and third branch ports. A hybrid LC/SAW high-pass filter is connected between the common port and the third branch port, a hybrid LC/SAW low-pass filter is connected between the common port and an internal node, an LC high-pass filter is connected between the internal node and the second branch port, and an LC low-pass filter is connected between the internal node and the first branch port.

It is claimed: 
     
       1. A communications device, comprising:
 a triplexer having a common port and first, second, and third branch ports; 
 wherein the triplexer comprises:
 a hybrid LC/SAW high-pass filter connected between the common port and the third branch port; 
 a hybrid LC/SAW low-pass filter connected between the common port and an internal node; 
 an LC high-pass filter connected between the internal node and the second branch port; and 
 an LC low-pass filter connected between the internal node and the first branch port. 
 
 
     
     
       2. The communications device of  claim 1 , wherein
 the hybrid LC/SAW low-pass filter and the LC low-pass filter are collectively configured to pass radio frequency signals in a frequency range of 450 MHz to 960 MHz between the common port and the first branch port,
 the hybrid LC/SAW low pass filter and the LC high-pass filter are collectively is configured to pass radio frequency signals in a frequency range of 1500 MHz to 2200 MHz between the common port and the second branch port, and 
 the hybrid LC/SAW high pass filter is configured to pass radio frequency signals in a frequency range above 2300 MHz between the common port and the third branch port. 
 
 
     
     
       3. The communications device of  claim 2 , further comprising:
 an antenna coupled to the common port; 
 a first radio coupled to the first branch port, the first radio configured to communicate over one or more channels within the frequency range of 450 MHz to 960 MHz; 
 a second radio coupled to the second branch port, the second radio configured to communicate over one or more channels within the frequency range of 1500 MHz to 2200 MHz; and 
 a third radio coupled to the third branch port, the third radio configured to communicate over one or more channels with frequencies above 2300 MHz. 
 
     
     
       4. The communications device of  claim 2 , wherein
 the hybrid LC/SAW low-pass filter is configured to pass radio frequency signals in a range from 450 MHz to 2200 MHZ and to stop radio frequency signals in a range from 2300 MHz to at least 4000 MHz, and 
 the hybrid LC/SAW high pass filter is configured to pass radio frequency signals in a frequency range from 2300 MHz to at least 4000 MHz and to stop radio frequency signals in a range from 450 MHz to 2200 MHZ. 
 
     
     
       5. The communications device of  claim 1 , wherein the hybrid LC/SAW high-pass filter comprises:
 an LC high-pass filter defining a stop-band and a pass-band separated by a transition frequency region; and 
 a SAW resonator connected in parallel with at least a portion of the LC high-pass filter, a resonance frequency of the first SAW resonator within the transition frequency region. 
 
     
     
       6. The communications device of  claim 5 , wherein
 the LC high-pass filter comprises two or more series capacitors and two or more shunt inductors, and 
 the SAW resonator is connected in parallel with at least one of the two or more series capacitors. 
 
     
     
       7. The hybrid LC/SAW high-pass filter of  claim 6 , wherein
 the LC high-pass filter comprises two series capacitors and two shunt inductors, 
 the first SAW resonator is connected in parallel with the two series capacitors, and 
 the hybrid LC/SAW filter further comprises a second SAW resonator connected in parallel with one of the shunt inductors. 
 
     
     
       8. The hybrid LC/SAW high-pass filter of  claim 6 , wherein
 the LC high-pass filter comprises four series capacitors and three shunt inductors, and 
 the first SAW resonator is connected in parallel with three of the series capacitors. 
 
     
     
       9. The communications device of  claim 1 , wherein the hybrid LC/SAW low-pass filter comprises:
 a bridged-T circuit including two inductors connected in series, a capacitor connected in parallel with the series-connected inductors, and a SAW resonator connected from a junction between the two inductors to ground. 
 
     
     
       10. The communications device of  claim 9 , further comprising:
 a second capacitor and a third inductor forming a low-pass filter section in series with the bridged-T circuit. 
 
     
     
       11. A hybrid LC/SAW high-pass filter comprising:
 an LC high-pass filter defining a stop-band and a pass-band separated by a transition frequency region, the LC high-pass filter comprising two or more series capacitors and two or more shunt inductors; and 
 a first SAW resonator connected in parallel with at least one of the two or more series capacitors, a resonance frequency of the first SAW resonator within the transition frequency region. 
 
     
     
       12. The hybrid LC/SAW high-pass filter of  claim 11 , wherein
 the LC high-pass filter comprises four series capacitors and three shunt inductors, and 
 the first SAW resonator is connected in parallel with three of the series capacitors. 
 
     
     
       13. The hybrid LC/SAW high-pass filter of  claim 11 , wherein
 the LC high-pass filter comprises two series capacitors and two shunt inductors, 
 the first SAW resonator is connected in parallel with the two series capacitors, and 
 the hybrid LC/SAW filter further comprises a second SAW resonator connected in parallel with one of the shunt inductors. 
 
     
     
       14. A hybrid LC/SAW low-pass filter defining a stop-band and a pass-band separated by a transition region, comprising:
 a bridged-T circuit including first and second inductors connected in series, a first capacitor connected in parallel with the series-connected first and second inductors; and 
 a shunt SAW resonator connected from a junction between the first and second inductors to ground, a resonance frequency of the shunt SAW resonator within the transition frequency region. 
 
     
     
       15. The hybrid LC/SAW low-pass filter of  claim 14 , further comprising:
 a second capacitor and a third inductor forming a low-pass filter section in series with the bridged-T circuit. 
 
     
     
       16. A communications device, comprising:
 a triplexer having a common port and first, second, and third branch ports; 
 wherein the triplexer comprises:
 a hybrid LC/SAW high-pass filter connected between the common port and the third branch port; 
 a hybrid LC/SAW low-pass filter connected between the common port and an internal node; 
 an LC high-pass filter connected between the internal node and the second branch port; and 
 an LC low-pass filter connected between the internal node and the first branch port, and 
 
 the hybrid LC/SAW high-pass filter comprises:
 an LC high-pass filter comprising two or more series capacitors and two or more shunt inductors, the LC high-pass filter defining a stop-band and a pass-band separated by a transition frequency region; and 
 a first SAW resonator connected in parallel with at least one of the two or more series capacitors, a resonance frequency of the SAW resonator within the transition frequency region. 
 
 
     
     
       17. The communications device of  claim 16 , wherein
 the LC high-pass filter comprises two series capacitors and two shunt inductors, 
 the first SAW resonator is connected in parallel with the two series capacitors, and 
 the hybrid LC/SAW filter further comprises a second SAW resonator connected in parallel with one of the shunt inductors. 
 
     
     
       18. The communications device of  claim 16 , wherein
 the hybrid LC/SAW low-pass filter and the LC low-pass filter are collectively configured to pass radio frequency signals in a frequency range of 450 MHz to 960 MHz between the common port and the first branch port, 
 the hybrid LC/SAW low pass filter and the LC high-pass filter are collectively configured to pass radio frequency signals in a frequency range of 1500 MHz to 2200 MHz between the common port and the second branch port, and 
 the hybrid LC/SAW high pass filter is configured to pass radio frequency signals in a frequency range above 2300 MHz between the common port and the third branch port. 
 
     
     
       19. The communications device of  claim 18 , further comprising:
 an antenna coupled to the common port; 
 a first radio coupled to the first branch port, the first radio configured to communicate over one or more channels within the frequency range of 450 MHz to 960 MHz; 
 a second radio coupled to the second branch port, the second radio configured to communicate over one or more channels within the frequency range of 1500 MHz to 2200 MHz; and 
 a third radio coupled to the third branch port, the third radio configured to communicate over one or more channels with frequencies above 2300 MHz. 
 
     
     
       20. The communications device of  claim 16 , wherein
 the LC high-pass filter comprises four series capacitors and three shunt inductors, and 
 the first SAW resonator is connected in parallel with three of the series capacitors. 
 
     
     
       21. A communications device, comprising:
 a triplexer having a common port and first, second, and third branch ports; 
 wherein the triplexer comprises:
 a hybrid LC/SAW high-pass filter connected between the common port and the third branch port; 
 a hybrid LC/SAW low-pass filter connected between the common port and an internal node; 
 an LC high-pass filter connected between the internal node and the second branch port; and 
 an LC low-pass filter connected between the internal node and the first branch port; and 
 
 wherein the hybrid LC/SAW low-pass filter comprises:
 a bridged-T circuit including two inductors connected in series, a capacitor connected in parallel with the series-connected inductors, and a SAW resonator connected from a junction between the two inductors to ground. 
 
 
     
     
       22. The communications device of  claim 21 , further comprising:
 a second capacitor and a third inductor forming a low-pass filter section in series with the bridged-T circuit. 
 
     
     
       23. The communications device of  claim 21 , wherein
 the hybrid LC/SAW low-pass filter and the LC low-pass filter are collectively configured to pass radio frequency signals in a frequency range of 450 MHz to 960 MHz between the common port and the first branch port, 
 the hybrid LC/SAW low pass filter and the LC high-pass filter are collectively configured to pass radio frequency signals in a frequency range of 1500 MHz to 2200 MHz between the common port and the second branch port, and 
 the hybrid LC/SAW high pass filter is configured to pass radio frequency signals in a frequency range above 2300 MHz between the common port and the third branch port. 
 
     
     
       24. The communications device of  claim 23 , further comprising:
 an antenna coupled to the common port; 
 a first radio coupled to the first branch port, the first radio configured to communicate over one or more channels within the frequency range of 450 MHz to 960 MHz; 
 a second radio coupled to the second branch port, the second radio configured to communicate over one or more channels within the frequency range of 1500 MHz to 2200 MHz; and 
 a third radio coupled to the third branch port, the third radio configured to communicate over one or more channels with frequencies above 2300 MHz.